The present invention relates to products for protecting the skin, in particular against attack by body discharges from weeping wounds (surgical or accident wounds) and/or by matter flowing out of stomata from the urinary or digestive tract, and very particularly to their application as pastes for forming a seal between the stomata and the appliances conventionally used.
In fact, it is important to protect either the skin which can be attacked by weeping surgical or accident wounds, or, around a stoma, the skin in contact with the urine (in the case of a ureterostomy) or with the stools (in the case of a colostomy and an ileostomy). As regards the stomata, they are not in fact all of a perfectly regular shape, and they have deep cavities, which are zones where the skin is not protected by the collecting appliance normally applied thereto.
Furthermore, the collecting appliances made available to patients with stomata have standardized orifice diameters which do not necessarily correspond to the actual size of the stoma to be fitted with the appliance.
Paste already exist on the market which are supposed to be able to act as a barrier to aggressive substances. However, these known pastes have certain disadvantages or prove difficult to use.
Thus, the pastes currently on the market contain an alcohol, a ketone or an ether as the main binder, and for this very reason must be contraindicated for irritated or sensitive skin.
French Pat. Nos. 78/16,326 and 78/16,615 describe adhesive compositions used for sealing stomata, which are based on natural or synthetic polymers but are in the form of discs and are therefore difficult to apply locally.
A paste (which is easy to apply and remove and which, once applied, protects the whole region of skin surrounding the wounds or the stoma against digestive acids and enzymes, alkaline stools, urine and other aggresive matter) having a novel formulation has now been found and developed. Furthermore, this paste has proved compatible with all bandages and all currently known systems for fixing collecting or draining bags (adhesive bags, bags with a Karaya seal and bags with a synthetic seal or support).
The present invention relates firstly to a paste for protecting the skin, which fundamentally comprises:
at least one hydrocolloid and/or another superabsorbent derived from hydrocolloids, insolubilized carboxymethylcellulose and a polyvinylpyrrolidone having a molecular weight of the order of 25,000 to 30,000, in particular as thickeners,
demineralized water as a binder, in combination with:
a suitable oil and a suitable stearate, and also
crosslinked and insolubilized polyvinylpyrrolidone, and advantageously,
sorbitol and/or polyethyleneglycol.
In a preferred embodiment, the essential components of the paste are in the following ratios and proportions by weight/weight:
powder/water: 1 to 3.5 approximately, preferably 1.5 to 1.9;
stearate/(water+oil+sorbitol and/or polyethyleneglycol).gtoreq.0.10, preferably about 0.15;
PVP/water: 0.5 to 2 approximately; and in another preferred embodiment:
% of PVPP.ltoreq.3% by weight/weight of the finished paste.
In these ratios, and also in the remainder of the present text, the term "powder" is understood as meaning all the pulverulent components mixed together, namely: the hydrocolloid, the insolubilized carboxymethylcellulose (abbreviated to CMC) and the polyvinylpyrrolidone (abbreviated to PVP); also, PVPP denotes the crosslinked and insolubilized polyvinylpyrrolidone.
A paste corresponding to a formulation of this type has proved exceptionally easy to apply and remove and, once applied to a region of skin containing a wound, or to the periphery of a stoma, is shown to protect, with an efficacy hitherto unknown, the whole of the region of skin surrounding the wound or the stoma against digestive acids and enzymes, alkaline stools, urine and other usual aggressive matter.
More generally, it seems, surprisingly, that a paste of this type can also be used as an inert carrier and/or vehicle for pharmaceutical compositions for the slow percutaneous administration of various active principles acting by transdermic diffusion (also called "transdermic" products). These transdermic products are currently known and used. It is clear that, in this type of application, the paste protects both the skin and the transdermic product itself against any external attack.
Furthermore, because the binding base of the paste is essentially demineralized water (whereas, in all the formulations currently on the market, it seems that the main binding base is an alcohol, a ketone or an ether), the paste according to the invention is not contraindicated for irritated skin as are the paste formulations currently on the market; by contrast, the paste according to the invention comprises a combination of aqueous binding base with oil (such as a paraffin oil or the like), forming an emulsion enabling another component of the formulation, namely the crosslinked and insolubilized polyvinylpyrrolidone, to utilize its film-forming properties which are particularly effective for rejuvenating damaged skin.
Moreover, the insolubilized carboxymethylcellulose (that is to say the carboxymethylcellulose crosslinked or insolubilized in any other way by methods know per se) seems to give the paste an exceptionally large absorption capacity for the moisture and the aqueous effluents discharged from the patient's body. Under the action of the moisture absorbed in this way, it gives the paste a high-viscosity gel texture and gives it the property of being able to change into a barrier impermeable to any external liquid phase, irrespective of the pH.
In addition to the essential or optional components indicated above, the paste according to the invention can also comprise secondary components chosen from amongst the conventional constituents and adjuvants, such as, in particular, preservatives, for example sorbic acid or the sodium salt or methyl para-hydroxybenzoate.
The hydrocolloid or mixture of hydrocolloids present in the paste according to the invention can be appropriately chosen by those skilled in the art from amongst the known hydrocolloids or formulated from several of the latter. These can be hydrocolloids extracted from plants (seeds or algae) or hydrocolloids synthesized by fermentation. Examples of hydrocolloids are guar, carob, alginates and carragheenins. Preference is given to alginates and very particularly to alkali metal alginates (especially sodium alginate), which are excellent thickeners, readily soluble and unlikely to create sealing zones in the medium to be thickened, and, more generally, any superabsorbent product, such as those formulated from hydrocolloids (for example the product marketed under the name Cecalgum by the Ceca Company and produced from alginic acid), can be used for the same purpose, either with the hydrocolloids or in place of them.
The insolubilized carboxymethylcellulose can be, for example, the product marketed under the name Aqualon by the Hercules France Company, which is a superabsorbent component. The polyvinylpyrrolidone having a molecular weight of the order of 25,000 to 30,000 is a very fine powder which, apart from its film-forming, bacteria-inhibiting and adhesive properties, makes it possible, in aqueous solution, to provide the paste with a good fluidity, by virtue of its very high binding capacity. All other things being equal, the proportion of this PVP powder relative to the water seems to have a great influence on the viscosity of the paste; to obtain a paste which is neither too fluid nor too thick, the ratio of PVP/water should in practice be kept between 0.5 and 2 approximately, preferably between 0.6 and 1.25 approximately.
The suitable oil and the suitable stearate and to fix the demineralized water, which is the binder for the paste, can be chosen respectively from amongst:
paraffin oil of Codex grade (France), such as, for example, a vaseline oil, which is in liquid form and emulsifies with the aqueous phase in the paste; and
a stearic acid fatty ester, such as, for example, glycol palmitostearate. In particular, glycol palmitostearate in combination with a polyoxyethyleneated fatty alcohol phosphate, which is in the form of a wax, can be used as an acid anionic gelling base for a water/oil mixture; it is a self-emulsifier. However, it is also possible to use other fatty alcohol stearates, such as, for example, the palmitostearate of glycerol and of polyoxyethylene glycol or the palmitostearate of ethylene glycol and of polyethylene glycol.
The crosslinked and insolubilized polyvinylpyrrolidone (PVPP) is a very fine powder having a high chemical inertness, adhesiveness in a moist environment, a high hydrophilicity, insolubility in aqueous media and good film-forming properties.
The paste according to the invention can moreover contain sorbitol and/or polyethylene glycol.
Sorbitol is in powder form; it constitues a binder complement in an aqueous phase and makes it possible, if desired, to reduce the amount of binder, which consists of water. In common practice, it is used in the form of a 70% aqueous solution and the amounts indicated below for the sorbitol correspond to amounts of a sorbitol solution of this type (referred to as aqueous sorbitol). Polyethylene glycol is a product which makes it possible, if desired, to improve the flow properties of the paste while at the same time making if possible to reduce the proportion of paraffin oil. It is in powder form for molecular weights of 4,000 to 6,000 and in liquid form for molecular weights of the order of 400.
If desired, it is possible to use one or other of these optional constituents, or both, the most appropriate grade being chosen in each case.
The respective proportions of the abovementioned constituents can be appropriately chosen by those skilled in the art, who can do this by carrying out routine experiments and can determine whether certain proportions initially suggested on an empirical basis are indeed suitable. In this respect, it is preferable to comply with the ratios of powder/water, stearate/(water+oil/sorbitol) and PVP/water, and also with the proportion of PVPP, which were indicated above as being advantageous. The amounts of each of the individual components are then either unrestricted or governed by these ratios and proportions.
As regards the possible addition of preservatives to this paste, it is preferred to use the pair comprising the sodium salt of methyl p-hydroxybenzoate and sorbic acid, which is a fungicide, of Codex grade (France), making it possible to have synergy at respective doses by weight of 1/1,000 and 0.5/1,000, relative to the weight of the paste. Of course, these preservatives are only mentioned as examples. The choice of preservatives is only governed by their French Codex registration and their intrinsic inhibitory power when they are combinated with the other constituents of the paste.
The process for the manufacture of the paste according to the invention uses techniques known to those skilled in the art; it can consist, for example, of one of the following two procedures: